Fix matplotlib warnings

[TomAugspurger]

This is with matplotlib 2.1.0

===================================================================== warnings summary ======================================================================
pandas/tests/plotting/test_frame.py::TestDataFramePlots::()::test_subplots_multiple_axes
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/plotting/_tools.py:204: UserWarning: When passing multiple axes, layout keyword is ignored
    "ignored", UserWarning)

pandas/tests/plotting/test_frame.py::TestDataFramePlots::()::test_line_colors
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/plotting/_core.py:188: UserWarning: 'colors' is being deprecated. Please use 'color'instead of 'colors'
    warnings.warn(("'colors' is being deprecated. Please use 'color'"

pandas/tests/plotting/test_frame.py::TestDataFramePlots::()::test_errorbar_plot
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/plotting/_core.py:1727: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    plot_obj.generate()
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/plotting/_core.py:1727: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    plot_obj.generate()
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/plotting/_core.py:1727: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    plot_obj.generate()

pandas/tests/plotting/test_frame.py::TestDataFramePlots::()::test_errorbar_timeseries
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/plotting/_core.py:1727: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    plot_obj.generate()
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/plotting/_core.py:1727: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    plot_obj.generate()
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/plotting/_core.py:1727: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    plot_obj.generate()

pandas/tests/plotting/test_hist_method.py::TestSeriesPlots::()::test_hist_legacy
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)

pandas/tests/plotting/test_hist_method.py::TestDataFramePlots::()::test_tight_layout
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/pandas/pandas/tests/plotting/test_hist_method.py:248: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    _check_plot_works(df.hist)

pandas/tests/plotting/test_misc.py::TestSeriesPlots::()::test_autocorrelation_plot
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)

pandas/tests/plotting/test_misc.py::TestDataFramePlots::()::test_andrews_curves
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)

pandas/tests/plotting/test_misc.py::TestDataFramePlots::()::test_parallel_coordinates_with_sorted_labels
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/axes/_base.py:2918: UserWarning: Attempting to set identical left==right results
  in singular transformations; automatically expanding.
  left=0, right=0
    'left=%s, right=%s') % (left, right))

pandas/tests/plotting/test_misc.py::TestDataFramePlots::()::test_radviz
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/pyplot.py:959: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    return gcf().gca(**kwargs)

pandas/tests/plotting/test_series.py::TestSeriesPlots::()::test_hist_legacy
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)
  /Users/taugspurger/Envs/pandas-dev/lib/python3.6/site-packages/matplotlib/cbook/deprecation.py:106: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    warnings.warn(message, mplDeprecation, stacklevel=1)

[jbrockmendel]

Still relevant?

[fangchenli]

Still many warnings. This is with matplotlib 3.3.1.

============================================================================================================================================== warnings summary ===============================================================================================================================================
pandas/tests/plotting/test_datetimelike.py::TestTSPlot::test_irreg_hf
pandas/tests/plotting/test_datetimelike.py::TestTSPlot::test_irreg_hf
pandas/tests/plotting/test_datetimelike.py::TestTSPlot::test_irreg_dtypes
pandas/tests/plotting/test_datetimelike.py::TestTSPlot::test_irreg_dtypes
pandas/tests/plotting/test_datetimelike.py::TestTSPlot::test_irreg_dtypes
pandas/tests/plotting/test_datetimelike.py::TestTSPlot::test_irreg_dtypes
pandas/tests/plotting/test_datetimelike.py::TestTSPlot::test_irreg_dtypes
pandas/tests/plotting/test_datetimelike.py::TestTSPlot::test_irreg_dtypes
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/core/frame.py:3204: FutureWarning: Automatically casting object-dtype Index of datetimes to DatetimeIndex is deprecated and will be removed in a future version.  Explicitly cast to DatetimeIndex instead.
    return klass(values, index=self.index, name=name, fastpath=True)

pandas/tests/plotting/test_frame.py::TestDataFramePlots::test_pie_df_nan
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/plotting/_matplotlib/core.py:1547: MatplotlibDeprecationWarning: normalize=None does not normalize if the sum is less than 1 but this behavior is deprecated since 3.3 until two minor releases later. After the deprecation period the default value will be normalize=True. To prevent normalization pass normalize=False 
    results = ax.pie(y, labels=blabels, **kwds)

pandas/tests/plotting/test_frame.py::TestDataFramePlots::test_errorbar_plot
pandas/tests/plotting/test_frame.py::TestDataFramePlots::test_errorbar_plot
pandas/tests/plotting/test_frame.py::TestDataFramePlots::test_errorbar_plot
pandas/tests/plotting/test_frame.py::TestDataFramePlots::test_errorbar_timeseries
pandas/tests/plotting/test_frame.py::TestDataFramePlots::test_errorbar_timeseries
pandas/tests/plotting/test_frame.py::TestDataFramePlots::test_errorbar_timeseries
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/plotting/_matplotlib/__init__.py:61: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    plot_obj.generate()

pandas/tests/plotting/test_hist_method.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_hist_method.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_hist_method.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_series.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_series.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_series.py::TestSeriesPlots::test_hist_legacy
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/tests/plotting/common.py:535: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    kwargs.get("ax", fig.add_subplot(211))

pandas/tests/plotting/test_hist_method.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_hist_method.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_hist_method.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_series.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_series.py::TestSeriesPlots::test_hist_legacy
pandas/tests/plotting/test_series.py::TestSeriesPlots::test_hist_legacy
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/tests/plotting/common.py:543: MatplotlibDeprecationWarning: Adding an axes using the same arguments as a previous axes currently reuses the earlier instance.  In a future version, a new instance will always be created and returned.  Meanwhile, this warning can be suppressed, and the future behavior ensured, by passing a unique label to each axes instance.
    kwargs["ax"] = fig.add_subplot(212)

pandas/tests/plotting/test_hist_method.py::TestSeriesPlots::test_hist_with_legend[b-2-expected_layout1]
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/plotting/_matplotlib/hist.py:354: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    axes = _grouped_hist(

pandas/tests/plotting/test_hist_method.py::TestDataFramePlots::test_tight_layout
pandas/tests/plotting/test_hist_method.py::TestDataFramePlots::test_hist_column_order_unchanged[None-expected0]
pandas/tests/plotting/test_hist_method.py::TestDataFramePlots::test_hist_column_order_unchanged[column1-expected1]
pandas/tests/plotting/test_hist_method.py::TestDataFramePlots::test_hist_with_legend[None-None]
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/tests/plotting/common.py:545: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    ret = f(**kwargs)

pandas/tests/plotting/test_hist_method.py::TestDataFramePlots::test_hist_subplot_xrot
pandas/tests/plotting/test_hist_method.py::TestDataFramePlots::test_hist_with_legend[None-c]
pandas/tests/plotting/test_hist_method.py::TestDataFramePlots::test_hist_with_legend[b-c]
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/plotting/_matplotlib/hist.py:396: UserWarning: To output multiple subplots, the figure containing the passed axes is being cleared
    axes = _grouped_hist(

pandas/tests/plotting/test_misc.py::TestSeriesPlots::test_autocorrelation_plot
pandas/tests/plotting/test_misc.py::TestSeriesPlots::test_autocorrelation_plot
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/plotting/_matplotlib/misc.py:443: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    ax = plt.gca(xlim=(1, n), ylim=(-1.0, 1.0))

pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_andrews_curves
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_andrews_curves
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_andrews_curves
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_andrews_curves
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_andrews_curves
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_andrews_curves
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_andrews_curves
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_andrews_curves
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/plotting/_matplotlib/misc.py:263: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    ax = plt.gca(xlim=(-np.pi, np.pi))

pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_radviz
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_radviz
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_radviz
pandas/tests/plotting/test_misc.py::TestDataFramePlots::test_radviz
  /home/fangchenli/Workspace/pandas-fangchenli/pandas/plotting/_matplotlib/misc.py:147: UserWarning: Requested projection is different from current axis projection, creating new axis with requested projection.
    ax = plt.gca(xlim=[-1, 1], ylim=[-1, 1])